Research is directed toward the question of the calcium function in arterial smooth muscle from animals with spontaneously hypertensive disease (SHR rats). Attention is focused on the availability of activator calcium involved in excitation-contraction coupling in aortic smooth muscle from SHR and normotensive rats. Several pharamacological probes are used to examine calcium releasibility and sequestration. The calcium ionophores such as X-537A and A23187 have been found to be useful agents in characterizing differences between SHR and normal arterial tissue. Other experiments are designed to reveal difference in relaxation of these arteries to agents which are inhibitors of calcium movements in smooth muscle (e.g., verapamil and diazoxide). Studies are being directed to direct measure of the calcium sequestering function of isolated microsomal vesicles obtained from arteries of SHR and normal rats. BIBLIOGRAPHIC REFERENCES: J. V. Levy. Verapamil and diazoxide antagonism of agonist-induced contractions of aortic strips from normal and spontaneously hypertensive rats (SHR). Res. Commun. Chem. Pathol. and Pharmacol. 11:387-404, 1975. J. V. Levy. Blood pressure changes in mature spontaneously hypertensive rats (SHR) following orally and subcutaneously administered beta-adrenergic receptor blocking drugs. Abst., VIth International Congress of Pharmacology, p.569, July, 1975.